I am getting a little exasperated by all this #metoo stuff.
This woman
http://www.bbc.co.uk/news/uk-england-bristol-41951618 says she has had unwanted attention from him for years and 'doesn't respond and hasn't encouraged him in any way'. But I wonder did he write to her in the way he did because she didn't put a stop to it?
If it had been going on for so long, why? A simple 'come on you silly boy stop it this isn't appropriate' a few times and 'would your wife like to see these letters' would likely have made him stop and think but to say nothing doesn't let him know you don't want the attention.
Did he regard it as 'office banter' and in view of not being told to stop it knew no better?
I'm not saying she hasn't been harassed in some way but if someone does something for many years without getting a slap (metaphorical or not) then why not?